The Cityzens thrashed the Portuguese giants in the first leg of their round of 16 showdown, but the manager was unhappy with certain aspects of their display.

Manchester City might have steamrolled past Sporting CP in the first leg of their UEFA Champions League round of 16 match-up, beating the Primeira Liga giants 5-0 away from home, but club manager Pep Guardiola was still left upset with aspects of his team's performance.

The Cityzens wasted no time in getting off the mark at the Estádio José Alvalade. Seven minutes was all they needed to break the deadlock as Riyad Mahrez put his team in team, albeit with a somewhat lengthy intervention from VAR. From then on, the reigning Premier League champions ran riot, with Bernardo Silva scoring a first-half brace, with his first goal being a thunderous volley, while Phil Foden also found the back of the net.

There was time for another goal in the second half as Raheem Sterling joined in on the fun, thus handing the English outfit an outstanding advantage ahead of the return leg at the Etihad Stadium. As a result, Manchester City were lavished with praise for their performance, and understandably so, with BT Sport pundit Owen Hargreaves stating that Guardiola's side are the closest team to perfection he has ever seen.

However, Pep saw things a tad differently. Speaking after the full-time whistle, the Spanish tactician argued that their display left room for improvement. What aspect, though, one might ask. The former Barcelona boss felt that his men were guilty of cheaply giving away possession in Tuesday's victory.

"We defend with the ball and we have to take care of the ball better than we did today," Guardiola told reporters, as per Marca.

"One of the principal rules I have is when you have the ball, try to pass the ball to the guy who wears the same shirt as you.

"This is the first [thing]. After, we will see what happens. When they are alone and lost the ball, it makes no sense and this happened many, many times.

"The difference between both teams was not 0-5, that's for sure.

"Today it was because we were so clinical, and when this happens it is mentally difficult for the opponent and you are more confident and relaxed."

Pep went into greater detail about his frustration with that performance, stressing that the VAR decision that went their way, on top of his players' proficiency in front of goal, played a huge role in securing that huge first-leg lead.

"Sometimes football is the margin of the first goal - offside or onside. When VAR took 30-45 seconds, I thought maybe the margin of offside was like this [closes thumb and finger]," he added.

"Sometimes the margin to win games is like that [gestures again] and all the analysis of how good one team is and how bad the other one is from that margin.

"Maybe you have this duty but I have another one to see how they perform individually as a team and if we did the plan well or not.

"Don't misunderstand me: it's a dream, a perfect result and so good for the second leg, but we can do better."

Pep is known as a perfectionist, and having pretty much secured a quarterfinal berth, the Spaniard probably has an eye on some of the bigger European teams they could face further down the competition. It will be interesting to see how far the Cityzens go in Europe this season.